1. Field of the Invention
This invention relates to a method for forming a resist pattern which is used in production of semiconductor devices and in which a photoresist containing a photoacid-generating acid is used.
2. Background Art
The method for producing a semiconductor device generally includes many steps for forming a desired pattern on a silicon wafer or a substrate to be treated in which a substance is stacked thereon as a film to be processed. In pattering of the substrate to be treated, first, a photoresist (photosensitive substance) containing a photoacid-generating agent is applied onto the substrate to be treated to form a photoresist film, and a predetermined region of the resist film is subjected to exposure. Next, exposed part of the photoresist film or non-exposed part thereof is removed by development treatment to form a resist pattern, and the substrate to be treated is etched so that the resist pattern serves as an etching mask.
Furthermore, there has been developed a multilayer resist process technique in which a lower layer film, an intermediate film, and an upper layer film (photoresist film) are formed on the substrate to be treated and the substrate to be treated is etched (see, for example, “Microfabrication Technique of Next Generation”, Toshiba Review, Vol. 59, No. 8 (2004), p 22-p 25 authored by Tokuhisa Oiwa).
As an exposure light source, an ultraviolet light such as KrF excimer laser or ArF excimer laser is used. However, as LSI is finer, required resolution has become less than the wavelength of the ultraviolet light, and the current condition is that exposure process capacity such as exposure amount capacity and focus capacity has been shorter.
As the semiconductor device is finer, dependency on the substrate to be treated of a profile of the resist pattern is larger, and this has become an obstacle of the device production or the further finer device. As one of causes of dependency on the substrate to be treated of a profile of the resist pattern, diffusion of chemical substance contained in the substrate to be treated into the resist can be thought. For the measures thereof, it can be thought to perform a resist design that a protective group with small detachment energy having little influence on the diffusion of chemical substance contained in the substrate to be treated into the resist is taken in a resist base resin. However, this method is in danger of inducing degradation of lithography performance of the resist and becoming an obstacle of production of the semiconductor device.